Marginal plots live on the “margins” of a main plot, adding extra information about the X and Y variables. In the example below, the marginals show how each group is distributed along each axis, complementing the relationships in the main plot.
Layouts
Marginal plots can be placed in different positions around the main plot, but they are most commonly shown on one side or two sides, most often above (x-axis) and to the right (y-axis).
They can also be layered, stacking multiple plot types on the same margin for richer context.
The main plot should always be the star
Marginal plots are there to provide complementary information, not to steal the spotlight.
Inventory
Marginal plots come in many forms. Histograms, boxplots, density curves, strip plots, and violins are common choices, though almost any plot type can be used. When you add more than one marginal, they can either match (same type) or be mixed (different types) to enrich the story. You can also layer them to add even more context.
More isn’t always better
Adding too many marginals can clutter your plot and overwhelm the reader.